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A concentrically corrugated near-field plate. The device consists of a coaxially fed central aperture surrounded by periodically spaced concentric grooves with nonperiodically varying depths. The focal plane is at a distance from the plate.
A subwavelength Airy function (ideal) and -directed electric-field focal patterns that approximate it. The frills plot represents the focal pattern produced by the computed magnetic frills, while the corrugated pattern represents the focal pattern formed by the lossless, concentrically corrugated near-field plate. The corrugated pattern shows a null-to-null beamwidth of at focal length , where . The corrugated and coaxial patterns are plotted for a frequency 1.143% above the design frequency (1 GHz). The inset shows the groove depths for a concentrically corrugated near-field plate.
The focal pattern produced by the concentrically corrugated near-field plate with copper boundaries (solid line) vs the focal pattern produced by a coaxial aperture in a copper ground plane with no corrugations. These results were computed using the commercial finite element electromagnetic solver COMSOL MULTIPHYSICS at a frequency 1.143% above the design frequency (1 GHz).
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